Conventionally, an inkjet printer has been known as an example of a liquid ejection apparatus. In general, with an inkjet printer, printing can be performed on a recording medium by ejecting ink, which is an example of a liquid, from a recording head onto a recording medium such as a sheet. Conventionally, a liquid supply system has been known as an ink supply means (liquid supply means) capable of supplying ink to this kind of printer (e.g., see PTL 1).